Apparatus for forming tubular blanks



Aug. 4, 1936. B. BANNISTER APPARATUS FOR FORMING TUBULAR BLANKS Filed April 20 1933 3 Sheets-Sheet 1 1720671502": EEYHNT' BQ/VN/STEE,

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APPARATUS FOR- FORMING TUBULAR BLANKS Filed April 20, 1933 3 Sheets-Sheet 2 u zorrUmm wzjmmm v Aug. 4, 1936. B. BANNISTER 2,050,236

APPARATUS FOR FORMING TUBULAR BLANKS Filed April 20/1933 3 Sheets-Sheet 3 I [Mei afar: BEYflNT BIQNNY/STEE,

Patented Aug. 4, 1936 UNITED STATES PATENT OFFIfiE Bryant Bannister, Mount Lebanon, Pa.

Application April 20, 1933, Serial No. 667,108

1 Claim.

This invention relates to the manufacture of seamless pipes and tubes from cast or round rolls, and more particularly to a novel form of piercing mill for forming a hollow and relatively thickwalled tube.

The usual piercing mill used for piercing a solid work-piece for subsequent rolling into seamless tubing of commercial dimensions operates to pierce and materially lengthen the same without changing its diameter appreciably. This operation is performed by passing the solid .work-piece between a pair of power-rotated, obliquely-disposed, barrel-shaped rolls which rotate and force the work-piece longitudinally over a conical mandrel or plug which is free to rotate but restricted from moving longitudinally. The work-piece is usually maintained in proper position between the work, or reducing, rolls by stationary guiding members located above and below the same. These guiding members offer considerable resistance to both rotational and longitudinal move ment of the work-piece.

In some cases the guiding members are of an improved type consisting of a pair of powerrotated guide rolls positioned intermediate the work rolls and with their mid-planes substantially coincident with the longitudinal axis of the mill. These rolls have a peripheral speed in the direction of and greatly in excess of the axial travel of the work-piece.

It is almost universal practice, at present, to follow the piercing operation by one or more sub sequent operations in order to further reduce the wall thickness without changing the diameter; and remove marks accruing from the contact of the tubular work-piece with the guide rolls referred to.

It is obvious to those skilled in the art that the least number of fabricating operations required, consistent, of course, with good and substantial yield of product, the lower the cost of production. The usual method employed to produce a seamless tube of good quality comprises a number of processing operations such as; initial piercing, second piercing, two passes of plug rolling, and reeling. The more improved method, in which power driven guide rolls are employed, comprises a piercing and elongating operation, performed on two separate mill units, and therefore requiring two crews of operators. In producing large diameter pipe, a first, and second or expanding-piercing operation is employed preceding the elongation operation.

It is obvious to those skilled in the art that if the reduction is made at too rapid a rate the metal is not displaced as uniformly as it would be at a slower rate and, therefore, dimensional and physical defects will result in the production.

An elongated reducing metal working pass in 5 combination with the usual fixed guides, for the purpose of preventing distortion, will result in excessive guide friction, and both quality of product accruing from twisting, etc., and also retarded rate of production would result. It has been found that the use of power driven guide rolls greatly reduces rotational and longitudinal friction, but if they are positioned with their contact areas in the conventional position; that is, with a line connecting their centers passing through the gorge, or end of the converging portion of the work roll pass, they permit too great an ovality, or distortion, at the outlet end of the pass and control of the diameter of the work-piece cannot be maintained, resulting in the metal of the work-piece which is displaced tangentially by the .metal working rolls being improperly displaced longitudinally.

According to the present invention, power actuated guide rolls are employed in combination with metal working rolls to form a roll pass having converging, elongated parallel, and diverging portions. The converging section is employed to grip the work-piece and rotate it while advancing it forwardly into the elongated parallel portion of the pass. This results in "necking down,of the solid work-piece, and is necessary to produce a grip sufficient to force the metal over the point of the piercing plug. The elongated parallel portion of the pass, and the associated piercing plug, are so disposed with respect to each other that substantially all of the displacement of metal by the metal working rolls occurs in this area.

In the' preferred. embodiment, the rearward portion. of the piercing plug is made cylindri al 4 g in order to be parallel to the rearward area of the elongated parallel portion of the pass and, therefore, provides a passsection whichreduces the wall of the pierced work-piece to a smooth and uniform thickness-with a slightly oval circumference. The diverging portion of the pass is immediately adjacent the parallel portion and functions solely to round-up the work-piece.

The piercing plug, which is associated with the metal working rolls to provide the novel metal working pass of the invention, is provided with a profile of such curvature and sopositioned with respect to the metalfworking roll contact surfaces that the shortest distance between it and the par-f allel portion of the pass in any transverse sec-" tion is greatest at the extreme point of the plug and decreases less rapidly as the section is moved rearwardly in the pass until the cylindrical portion of the piercing plug is parallel to the face of the metal working rolls.

In the present invention, the power driven guide rolls are disposed with their contact areas substantially adjacent that section of the pass wherein the last wall reduction is made. In addition to functioning in combination with the metal working rolls to accurately control the diameter of the pierced work-piece, the guide rolls, positioned as described, present a comparatively fiat surface parallel to the cylindrical portion of the piercing plug, where the last wall reduction is made. This condition could not, of course, exist if the guide rolls were placed with their contact area forwardly in the pass.

One object of the present invention is the provision of a novel apparatus to completely fabricate finally finished seamless pipes or tubes in a single operation.

Another object is to provide a novel apparatus for obtaining an extremely orderly movement of the metal of the work-piece while effecting a very substantial displacement.

Still another object of the invention is to provide novel means for providing a great many contacts of the various metal working surfaces with successive increments of metal of the workpiece.

A further object is the provision of novel means for producing seamless pipes and tubes in which the displacement or flow of the metal will be well distributed in such manner as to obviate excessive distortion, or stresses and abuse, of the metal of the work-piece and the various parts of the mill.

A still further object is to provide for the most substantial reduction in billet, or work-piece, cross-sectional area in the early stages of reduction and less at the final stages thereof, resulting in the extremely fine finish of the product, free from the usual helical waves and other defects and imperfections.

The above and still further objects will be apparent after referring to the drawings, in which:

Figure 1 is a plan of the apparatus of the invention with the top power actuated guide roll removed, and showing the work-piece in section.

Figure 2 is an end elevation of the apparatus from the introductory end thereof.

Figure 3 is a composite view disclosing the relationship'of one metal working roll to one of the guide rolls which is shown together with a portion of the work-piece, in a plane substantially degrees from its true position in the mill.

Figure 4 is a plan similar to Figure 1, but showing a modified piercing plug.

Figure 5 is a composite view similar to Figure 3, but showing the modified piercing plug of Figure 4.

Referring more particularly to the drawings, the numeral 2 designates a pair of barrel-shaped metal working rolls which are mounted on axes substantially parallel to one another and to the center line of the pass they are intended to define, but are oppositely inclined with respect to the vertical. The metal working rolls 2 when taken together provide converging surfaces 2 elongated parallel surfaces 2 and diverging surfaces 2. The elongated parallel surfaces 2*, of the metal working rolls, are of greater length than the diameter of the blank to be processed.

A pair of power actuated guide rolls 3 are disposed with their contact areas intermediate the metal working rolls 2, and rotate on axes at substantial right angles with respect to the line of pass defined by the former.

The conical piercing plug of the invention is generally indicated at 4 and provided wth a rearward cylindrical portion 4. The piercing plug 4 is mounted on a mandrel bar 5 and positioned with its point slightly in the converging portion of the pass defined by the surfaces 2 of the metal working rolls 2.

In practice, the peripheries of the guide rolls 3 are intended to present contact areas in conjunction with most of the parallel portion of the pass defined by the elongated parallel surfaces 2 of the metal working rolls. That is to say, the guide 15 rolls 3 are intended to contact with the pierced portion of the work-piece after its introduction to the parallel portion of the pass and continue this relationship to substantially the end of this area. 20

In operation, a solid work-piece 6 is introduced into the converging portion of the pass where it is necked-down and forced over the point 4 of the piercing plug, which is given a slight lead or, in other words, disposed to extend slightly into 25 this portion. As the metal of the work-piece is worked between the elongated parallel portion of the pass defined by the surfaces 2 of the metal working rolls and the piercing plug 4, a very substantial reduction in wall thickness will occur, 30 while the tangential flow of the metal is restrained from excessive distortion, or ovality, and diverted longitudinally by the rapidly rotating contact areas of the guide rolls 3.

The metal of the work-piece will next be intro- 35 duced between the cylindrical portion 4 of the piercing plug and the last area of the elongated parallel surfaces 2 of the metal working rolls while still in contact with the surfaces of the guide rolls. A very effecting reeling action will occur in this portion of the pass and the pierced work-piece will emerge therefrom with a finely finished surface and slightly oval circumference.

The action of the guide rolls to divert succes sive increments of metal of the work-piece from a tangential movement into a longitudinal movement will cease shortly after the work-piece enters the reeling section.

The slightly oval circumference of the workpiece will be effectively "rounded-up in the diverging portion of the pass defined by the surfaces 2 of the metal working rolls, from whence it will emerge from the mill in finally finished form and having the characteristics hereinbefore referred to.

In Figures 4 and 5 of the drawings, there is disclosed a modified form of the invention which is adapted for piercing operations electively intended to be followed by subsequent processing. Under these circumstances, of course, reeling would 60 be unnecessary, as "waviness in the surface of the work-piece would not be objectionable. Accordingly, there is provided a tapered piercing plug 1 of a design similar to the plug 4 of the preferred embodiment, except that the rearward 65 portion thereof is not cylindrical. The plug I is mounted on a mandrel bar 8 and disposed in the same relative position with respectto the metal working rolls 2 and guide rolls 3, as would be the plug 4.

In operation, the work-piece 6 will be processed exactly as in the preferred embodiment of the invention, except that internal support ofiered by the piercing plug I will cease a short distance before the cessation of contact of the guide rolls 3. 75 i This will have no effect on the wall of the workpiece other than that it will not be reeled.

It is to be understood that I do not wish to be limited to a plurality of metal working rolls having accurately parallel elongated portions, as the invention contemplates slight variations, and while I have shown and described one specific embodiment I do not wish to be limited exactly thereto, since various modifications may be made without departing from the scope of my invention, as defined in the following claim.

I claim:

Apparatus for forming tubular blanks comprising a plurality of metal working mils defining a pass. each of said rolls being provided with a convergent portion, an elongated substantially parallel portion which extends from the gorge of the pass rearwardiy throughout the entire metal working zone, and a divergent portion, a mandrel disposed in the pass formed by said plurality of metal working rolls, in combination with at least one power-actuated guide roll disposed intermediate said metal working roils and with its contact surface nearest the longitudinal center-line of the pass adjacent the exit end of the elongated 10 

